11,718 research outputs found
Detection of the large scale alignment of massive galaxies at z~0.6
We report on the detection of the alignment between galaxies and large-scale
structure at z~0.6 based on the CMASS galaxy sample from the Baryon Oscillation
Spectroscopy Survey data release 9. We use two statistics to quantify the
alignment signal: 1) the alignment two-point correlation function which probes
the dependence of galaxy clustering at a given separation in redshift space on
the projected angle (theta_p) between the orientation of galaxies and the line
connecting to other galaxies, and 2) the cos(2theta)-statistic which estimates
the average of cos(2theta_p) for all correlated pairs at given separation. We
find significant alignment signal out to about 70 Mpc/h in both statistics.
Applications of the same statistics to dark matter halos of mass above 10^12
M_sun/h in a large cosmological simulation show similar scale-dependent
alignment signals to the observation, but with higher amplitudes at all scales
probed. We show that this discrepancy may be partially explained by a
misalignment angle between central galaxies and their host halos, though
detailed modeling is needed in order to better understand the link between the
orientations of galaxies and host halos. In addition, we find systematic trends
of the alignment statistics with the stellar mass of the CMASS galaxies, in the
sense that more massive galaxies are more strongly aligned with the large-scale
structure.Comment: 6 pages, 3 figures, accepted for publication in ApJ Letter
We\u27re in Charge of What We\u27re Saying, What We Discuss, What We Want to Read : A Qualitative Inquiry Into Adolescent Girls\u27 After-School Book Clubs
This qualitative study examines the ways in which 23 early adolescent and adolescent girls and their literacy teacher co-constructed, participated in, and experienced an after-school book club located in a school setting. The book club met biweekly to discuss a student-selected text (e.g., fiction, non-fiction, song lyrics) over the course of one academic year. Using ethnographic methods, I explored what happened in the after-school book club, and how the girlsâ race, gender, and class identities informed their readings of texts and emerged in their talk.
From the data I identified several critical themes and learnings. First, the girls understood, talked about, and practiced reading as deeply relational and embedded in human relationships. Social relationships, family networks, and peer groups were identified as important factors that motivated the girls to read, and that sustained the girlsâ commitment to reading. Second, the social aspect of book clubsâreading with othersâfostered critical readings of and deeper engagement with texts. In and through reading and talking together, the girls reflected on, questioned, and debated the role of race, gender, and class. The girls also initiated and sustained conversations that reflected the ways in which they understood themselves, other people, and their worlds. As readers the girls assumed a critical inquiry stance, inquiring into and grappling with difficult social and economic realities. Third, the girls assumed a range of roles and responsibilities for forming and sustaining the book club. Lastly, the girls demonstrated their understanding of in-school and out-of-school contexts as reciprocalâi.e., that texts, social practices, knowledge and identities travel between and across contexts.
The implications emerging from this study are relevant to the work of teachers, researchers, literacy-curriculum writers, after-school program coordinators, and others committed to supporting adolescent learners in both in-school and out-of-school settings. This study can prompt educators to re-imagine and reconstruct learning environmentsâboth in and out of schoolâthat can engage, challenge, and inspire adolescent learners. It can also generate conversation within the education research community about the possibilities and challenges involved in studying after-school spaces of literacy learning and engagement
Secure Quantum Secret Sharing Based on Reusable GHZ States as Secure Carriers
We show a potential eavesdropper can eavesdrop whole secret information when
the legitimate users use secure carrier to encode and decode classical
information repeatedly in the protocol [proposed in Bagherinezhad S and
Karimipour V 2003 Phys. Rev. A \textbf{67} 044302]. Then we present a revised
quantum secret sharing protocol by using Greenberger-Horne-Zeilinger state as
secure carrier. Our protocol can resist Eve's attack
Taste and Visual Influences on Hispanic Consumers' Preferences and Willingness-to-Pay for Pasture-Fed Beef
Experimental Economics methods are used to determine Hispanic consumersâ sensory acceptance of pasture-fed beef and evaluate visual and taste influences on their overall preferences and willingness-to-pay (WTP). Two hundred and thirty-one Hispanic consumers in four experimental sites in Virginia participated in a laboratory experimental procedure where they visually examined and tasted pasture-fed and conventionally produced grain-fed beef, and then participated in a non-hypothetical Multiple Price Lists (MPL) experiment to determine their WTP. Hispanic consumers perceived significant differences between pasture-fed and grain-fed beefâs appearance and taste. Visual and taste acceptances are closely correlated to and significantly influence overall preferences. More than fifty percent of Hispanic consumers prefer pasture-fed beef and the majority of them consistently are willing to pay a price premium. Approximately, half consumers who generally prefer pasture-fed beef consistently consider the appearance and taste of pasture-fed beef more favorable but another half of them indicated discrepant visual and taste acceptances. Nevertheless, this inconsistency doesnât lead to a lower WTP for pasture-fed beef.Pasture-Fed Beef, Experimental Economics, Multiple Price Lists, Preference, Willingness-to-pay, Agribusiness, Consumer/Household Economics, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Livestock Production/Industries, Marketing,
Seeing many-body effects in single- and few-layer graphene: Observation of two-dimensional saddle-point excitons
Significant excitonic effects were observed in graphene by measuring its
optical conductivity in a broad spectral range including the two-dimensional
{\pi}-band saddle-point singularities in the electronic structure. The strong
electron-hole interactions manifest themselves in an asymmetric resonance
peaked at 4.62 eV, which is red-shifted by nearly 600 meV from the value
predicted by ab-initio GW calculations for the band-to-band transitions. The
observed excitonic resonance is explained within a phenomenological model as a
Fano interference of a strongly coupled excitonic state and a band continuum.
Our experiment also showed a weak dependence of the excitonic resonance in
few-layer graphene on layer thickness. This result reflects the effective
cancellation of the increasingly screened repulsive electron-electron (e-e) and
attractive electron-hole (e-h) interactions.Comment: 9 pages, 3 figures, In PR
Electronic Structure in Gapped Graphene with Coulomb Potential
In this paper, we numerically study the bound electron states induced by long
range Coulomb impurity in gapped graphene and the quasi-bound states in
supercritical region based on the lattice model. We present a detailed
comparison between our numerical simulations and the prediction of the
continuum model which is described by the Dirac equation in (2+1)-dimensional
Quantum Electrodynamics (QED). We also use the Fano's formalism to investigate
the quasi-bound state development and design an accessible experiments to test
the decay of the supercritical vacuum in the gapped graphene.Comment: 5 page, 4 figure
Intragenic homogenization and multiple copies of prey-wrapping silk genes in Argiope garden spiders.
BackgroundSpider silks are spectacular examples of phenotypic diversity arising from adaptive molecular evolution. An individual spider can produce an array of specialized silks, with the majority of constituent silk proteins encoded by members of the spidroin gene family. Spidroins are dominated by tandem repeats flanked by short, non-repetitive N- and C-terminal coding regions. The remarkable mechanical properties of spider silks have been largely attributed to the repeat sequences. However, the molecular evolutionary processes acting on spidroin terminal and repetitive regions remain unclear due to a paucity of complete gene sequences and sampling of genetic variation among individuals. To better understand spider silk evolution, we characterize a complete aciniform spidroin gene from an Argiope orb-weaving spider and survey aciniform gene fragments from congeneric individuals.ResultsWe present the complete aciniform spidroin (AcSp1) gene from the silver garden spider Argiope argentata (Aar_AcSp1), and document multiple AcSp1 loci in individual genomes of A. argentata and the congeneric A. trifasciata and A. aurantia. We find that Aar_AcSp1 repeats have >98% pairwise nucleotide identity. By comparing AcSp1 repeat amino acid sequences between Argiope species and with other genera, we identify regions of conservation over vast amounts of evolutionary time. Through a PCR survey of individual A. argentata, A. trifasciata, and A. aurantia genomes, we ascertain that AcSp1 repeats show limited variation between species whereas terminal regions are more divergent. We also find that average dN/dS across codons in the N-terminal, repetitive, and C-terminal encoding regions indicate purifying selection that is strongest in the N-terminal region.ConclusionsUsing the complete A. argentata AcSp1 gene and spidroin genetic variation between individuals, this study clarifies some of the molecular evolutionary processes underlying the spectacular mechanical attributes of aciniform silk. It is likely that intragenic concerted evolution and functional constraints on A. argentata AcSp1 repeats result in extreme repeat homogeneity. The maintenance of multiple AcSp1 encoding loci in Argiope genomes supports the hypothesis that Argiope spiders require rapid and efficient protein production to support their prolific use of aciniform silk for prey-wrapping and web-decorating. In addition, multiple gene copies may represent the early stages of spidroin diversification
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